Uranium Mineral Particles Produced by Weathering in Sierra Peña Blanca, Chihuahua, Mexico: A Synchrotron-Based Study

• DOI: 10.20944/preprints202502.1817.v1
• Publication Date: 2025-02-27T05:19:51Z
• Authors: Cristina Hernánde...; Jesús G. Canché-T...; Yair Rodríguez-Gu...; Fabián G. Faudoa-...; Konstantin Ignatyev; Diane M. Eichert; Rocío M. Cabral-L...; Victoria Pérez-Reyes; Hilda E. Esparza-...; María-Elena Monte...

Some of the largest uranium deposits in Mexico are located in Chihuahua. The most important is in Sierra Peña Blanca, northwest of the capital, which was explored and partially exploited in the 1980s. After the closure of activities, the mining projects were left exposed to weathering. To characterize the drift of uranium minerals towards the neighboring Laguna del Cuervo, sediment samples were collected in the main streams in the drainage pattern of the largest deposits. The uranium mineral fragments from the fine sand portion were extracted using fluorescence at 365 nm light. These particles' morphology and elemental composition were analyzed by focused ion beam microscopy (FIB) and scanning transmission electron microscopy (STEM). The particle density in samples close to the uranium sources was quantified using gamma spectrometry. The highest density was 2500 part./g, and the lowest was 124 part./g. X-ray absorption spectrometry (XAFS) allowed to establish the speciation of U in the urani-um particles, confirming U(VI) through the XANES spectrum. Theoretical fitting of the EXAFS spectrum confirmed the presence of uranophane. Finally, the Fe, Sr, and U dis-tribution in the particle and its matrix was obtained by X-ray fluorescence microto-mography (CT-µXRF). It was concluded that the particle is composed of uranophane, imbricated with quartz and other oxides.